Field of the Invention
The invention is related in general to implantable prostheses and in particular to stent-grafts.
Related Art
Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts constructed of biocompatible materials have been employed to replace or bypass damaged or occluded natural blood vessels. In general, endovascular grafts typically include a graft anchoring component that operates to hold a tubular graft component of a suitable graft material in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in situ to anchor the tubular graft component to the wall of a blood vessel or anatomical conduit. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the opposition forces provided by the radially expandable stents.
Grafting procedures are also known for treating aneurysms. Aneurysms result from weak, thinned blood vessel walls that “balloon” or expand due to aging, disease and/or blood pressure in the vessel. Consequently, aneurysmal vessels have a potential to rupture, causing internal bleeding and potentially life threatening conditions. Grafts are often used to isolate aneurysms or other blood vessel abnormalities from normal blood pressure, reducing pressure on the weakened vessel wall and reducing the chance of vessel rupture. As such, a tubular endovascular graft may be placed within the aneurysmal blood vessel to create a new flow path and an artificial flow conduit through the aneurysm, thereby reducing if not nearly eliminating the exertion of blood pressure on the aneurysm.
In general, rather than performing an open surgical procedure to implant a bypass graft that may be traumatic and invasive, endovascular grafts which may be referred to as stent-grafts are preferably deployed through a less invasive intraluminal delivery procedure. More particularly, a lumen or vasculature is accessed percutaneously at a convenient and less traumatic entry point, and the stent-graft is routed through the vasculature to the site where the prosthesis is to be deployed. Intraluminal deployment is typically effected using a delivery catheter with coaxial inner and outer tubes arranged for relative axial movement. For example, a self-expanding stent-graft may be compressed and disposed within the distal end of an outer catheter tube distal of a stop fixed to the inner member. The catheter is then maneuvered, typically routed through a body lumen until the end of the catheter and the stent-graft is positioned at the intended treatment site. The stop on the inner member is then held stationary while the outer tube of the delivery catheter is withdrawn. The inner member prevents the stent-graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent-graft is released from the confines of the sheath and radially self-expands so that at least a portion of it contacts and substantially conforms to a portion of the surrounding interior of the lumen, e.g., the blood vessel wall or anatomical conduit.
In recent years to improve alignment during deployment of a stent-graft having self-expanding stents, various tip capture mechanisms have been incorporated into the delivery system used for percutaneously delivering the prosthesis. For example, U.S. Patent Application Publication No. 2006/0276872 to Arbefuielle et al. and U.S. Patent Application Publication No. 2009/0276207 to Glynn et al., both herein incorporated by reference in their entirety, describe tip capture mechanisms that restrain the proximal end stent of the stent-graft while the remainder of the stent-graft expands, then releases the proximal end stent. The proximal end stent is attached to the graft material of the stent-graft so as to have an “open web” or “free flow” proximal end configuration in which the endmost crowns thereof extend past or beyond the graft material such that the endmost crowns are exposed or bare, and thus free to interact with a tip capture mechanism and couple the prosthesis to the delivery system. The open web proximal end configuration allows blood flow through the endmost crowns for perfusion during and/or after implantation. FIGS. 1A and 1B illustrate a delivery system 10 having a tip capture mechanism 12 designed to couple or interact with a stent-graft 14 having an open web or free flow proximal end configuration 16. More particularly, endmost crowns 18 engage or hook around retractable finger or prong-like elements 20 of the tip capture mechanism. When an outer delivery shaft 22 is retracted to allow stent-graft 14 to self-expand, endmost crowns 18 of the end stent 15 remain hooked around tip capture fingers 20, as shown in FIG. 1A. To release end stent 15, a shaft 24 coupled to finger or prong-like elements 20 is retracted and end stent 15 is allowed to self-expand, as shown in FIG. 1B. The Captivia Delivery System manufactured by Medtronic Vascular, Inc. of Santa Rosa, Calif. is one example of a delivery system having a tip capture mechanism as described above, which may be used for delivering endovascular stent-grafts such as the Valiant Thoracic Stent-graft manufactured by Medtronic Vascular, Inc. of Santa Rosa, Calif.
Tip capture mechanisms have improved accuracy of deployment of self-expanding stent-grafts having open web or free flow configurations. However, in some cases a closed web configuration may be required or chosen due to application and/or user preferences. In a closed web configuration, the endmost crowns do not extend past or beyond the graft material but rather are covered by graft material. Embodiments hereof relate to a stent-graft having a closed web configuration that may interact with a tip capture mechanism of a delivery system.